1. Field of Disclosure
The present disclosure relates generally to improvements in laser scanning bar code symbol reading systems, at point-of-sale (POS) environments and elsewhere, with increased scanning flexibility and high throughput.
2. Brief Description of the State of Knowledge in the Art
Typically, omni-directional laser scanning bar code symbol readers employ a regular polygon shape which produces a consistent, uniform raster laser scanning pattern through a certain sweep angle. For example, a common scanning polygon has an approximate square profile producing a 4-line raster through nearly 180 degrees of sweep. The deficiency in this uniform raster is that when the laser scanning lines are folded into an intersecting 3D scanning volume for omni-directional performance, all field angles experience the same number of laser scanning lines. This is not optimal for uniform omni-directional performance.
Typically, bar codes in a “picket fence” orientation (i.e. bars and spaces oriented parallel to the direction of code motion) are more easily scanned, thereby requiring fewer scan lines to do a good scanning job. As the code orientation changes, and tends toward a “ladder” orientation (i.e. bars and spaces oriented perpendicular to the direction of code motion), more scanning lines are required to maintain the same level of performance.
In NCR's 7878 bioptic laser scanning bar code symbol reader, a single, centered laser and a 6-sided irregular polygon is employed to produce an approximate 180 degree sweep (i.e. scanning region), wherein the center third of the scanning region consists of 6 scanning lines, and the left and right third scanning regions each consist of only 3 scanning lines. While the NCR prior art system employs non-uniform scan density with respect to line orientation, in an attempt to provide a more robust scanning pattern, its scan density is not sufficiently non-uniform with respect to line orientation, in many applications, and consequently, scanning performance is compromised.
Thus, there is still a great need in the art for improved bi-optical laser scanning bar code symbol reading system which is capable of high-performance, and robust operations in demanding POS scanning environments, while avoiding the shortcomings and drawbacks of prior art systems and methodologies.